Other technetium isotopes are not produced in significant quantities by fission; when needed, they are manufactured by neutron irradiation of parent isotopes (for example, 97Tc can be made by neutron irradiation of 96Ru).

In 1962, technetium-99 was isolated and identified in pitchblende from the Belgian Congo in very small quantities (about 0.2 ng/kg); there it originates as a spontaneous fission product of uranium-238.